Aug. 28, 2013

A necropsy technician at Penn Vet's New Bolton Center in Kennett Square, Pa., weighs a dead dolphin while a second bottlenose dolphin is set on a table to be examined. Photo courtesy of University of Pennsylvania's School of Veterinary Medicine, New Bolton Center / Photo courtesy of University of Pennsylvania

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A measles-like virus is most likely responsible for 357 bottlenose dolphin deaths recorded through Monday of this year from New York to North Carolina, according to federal officials.

Other factors may have weakened the dolphins’ immune systems, making them more vulnerable to sickness. They include chemicals, other disease-causing microbes, biotoxins and expansion of the dolphins’ range, according to officials and experts. The investigation is ongoing.

The dolphin die-off — called an unusual mortality event — comes a quarter-century after 742 bottlenose dolphins were discovered along the shores of New Jersey to Florida. Morbillivirus was eventually linked to their deaths in 1987-88, according to officials.

New Jersey death toll

This year’s death toll in New Jersey is 72 through Monday, according to Maggie Mooney-Seus, spokeswoman for NOAA Fisheries.

But Robert Schoelkopf, director of the Marine Mammal Stranding Center in Brigantine, said he has counted 74 since July 9, the most recent of which was a badly decomposed, shark-scavenged dolphin carcass found at Cape May Point on Monday.

This year’s episode is “very similar to what we saw in 1987,” Schoelkopf said. “Very few people that are in the business right now were around in ’87 to see that die-off. We were the first in ’87, as we were this time, (to tell) everybody that we’re finding something unusual.”

Morbilliviruses are usually spread through inhalation or contact between animals, including mothers and calves, according to NOAA. Animals can also be exposed to the virus through the eyes, mouth, stomach, skin wounds and the urogenital tract.

Symptoms include weight loss, skin lesions, pneumonia and brain and other infections, according to NOAA.

Rowles said “many of the dolphins younger than 26 years old have limited to no immunity to this virus.”

Virus could spread

There is a risk that the virus may be spreading from other marine mammal species and researchers are looking into other strandings over the last six months or so, she said.

According to NOAA, the virus cannot be transmitted to humans and no cases of human illness have been reported from this dolphin disease outbreak.

“There is no indication that this particular virus could jump into humans,” said Dr. Jerry Saliki of the University of Georgia.

But bottlenose dolphins are wild animals that may injure people if approached closely, and NOAA urges people to avoid dead or live marine mammals on the beach or floating in coastal waters.

People also should not swim with open wounds or in the immediate area where a stranded animal is found, according to NOAA. It is unclear if people could get any infectious diseases by touching the sick dolphins, but people and dolphins share a vulnerability to disease-causing microbes.

People should also keep pets away from marine mammals, especially stranded live or dead ones, according to NOAA.

From Jan. 1 through Sunday, 488 dolphins have been found stranded from New York to North Carolina, according to NOAA.

But Dr. Margaret L. Lynott of the Virginia Aquarium & Marine Science Center said they’ve “definitely gotten reports of floating carcasses that we were not able to remove and there are plenty of those.”

No vaccine

Rowles said “at this point, there isn’t anything that we can do to stop the virus. We don’t have a vaccine that is developed that could be easily deployed in a wild population of bottlenose dolphins or subpopulation of bottlenose dolphins at this point.”

Evaluations will continue over the next several months as new animals are found or new evidence guides the investigation, according to NOAA.

Rowles said bottlenose dolphins along the coast “do have high levels of polychlorinated biphenyls and other chemicals that could have an impact on immune function.”

Brucella bacteria, which are common in marine mammals, have also been found in joint, brain or reproductive organ lesions in four dolphins so far, according to NOAA. The agency has been investigating Brucella in marine mammal populations in the U.S. since 2011.